Processes for manufacture of molecular sieves

ABSTRACT

Colloidal crystalline molecular sieve seeds are used in phosphorus-containing crystalline molecular sieve manufacture. Certain of the products have enhanced utility in oxygenate conversions.

This invention relates to molecular sieves and processes for theirmanufacture. More especially it relates to processes in which synthesismixtures are seeded to control process conditions and productcharacteristics. The invention relates primarily to the manufacture ofphosphorus-containing molecular sieves.

It is well-known that seeding a molecular sieve synthesis mixturefrequently has beneficial effects, for example in controlling theparticle size of the product, avoiding the need for an organic template,accelerating synthesis, and improving the proportion of product that isof the intended structure type.

In U.S. Pat. No. 4,440,871, the preparation of a number ofphosphorus-containing molecular sieves is described, and it is statedthat the crystallization procedure may be facilitated by stirring, orother moderate agitation of the synthesis mixture, or by seeding it withcrystals of the molecular sieve to be produced or one of a topologicallysimilar structure.

The patent particularly describes processes for the manufacture ofnumerous crystalline microporous silicoaluminophosphates (SAPO's)including SAPO-34, employing sources of silicon (e.g., a silica sol),aluminium (e.g., hydrated aluminium oxide), and phosphorus (e.g.,orthophosphoric acid), and an organic template, for exampletetraethylammonium hydroxide (TEAOH), isopropylamine (iPrNH₂) ordi-n-propylamine (DPA). The patent, the disclosure of which isincorporated by reference herein, gives X-ray diffraction data for theSAPO's and describes their utilities in catalysis and absorption.

It has now been found that advantages result from the use of colloidalseeds in the manufacture of phosphorus-containing molecular sieves.

The present invention accordingly provides in a first aspect a processfor the manufacture of a crystalline molecular sieve containingphosphorus in its framework, which process comprises treating asynthesis mixture comprising elements necessary to form thephosphorus-containing molecular sieve and colloidal crystallinemolecular sieve seeds for a time and at a temperature appropriate toform the desired molecular sieve.

It has surprisingly also been found that the seed crystals may be of astructure type different from that of the desired molecular sieve. Suchseeding may be regarded as “heterostructural”, whereas seeding withseeds of the same structure type is termed “isostructural”, whether ornot the seeds are of the same composition (i.e., contain the sameelements in the same proportions) as the crystalline molecular sieve tobe produced.

Where the seeds are of a structure type different from those of thedesired molecular sieve, advantageously the seeds and the desiredmolecular sieves are topologically similar, for example are members ofthe ABC-6 group of materials, as described in “Topochemistry of Zeolitesand Related Materials”, J. V. Smith, Chem. Rev. 1988, 88, 149 at 167,the disclosure of which review article is incorporated herein byreference. The ABC-6 group includes, inter alia, the Offretite,Chabazite and Levyne structures.

As used in this specification, the term “structure type” is used in thesense described in the Structure Type Atlas, Zeolites 17, 1996.

The present invention accordingly provides in a second aspect a processfor the manufacture of a crystalline molecular sieve containingphosphorus in its framework, which comprises treating a synthesismixture comprising elements necessary to form a phosphorus-containingmolecular sieve of a first structure type and colloidal molecular sieveseed crystals of a second, different, structure type, for a timesufficient and at a temperature appropriate to form the molecular sieveof the first structure type.

In further aspects, the invention provides the use, in the synthesis ofa phosphorus-containing crystalline molecular sieve, of colloidal seedcrystals to control the particle size of the product, or to acceleratethe formation of the product, or both to control the particle size andaccelerate the formation of the product.

As the phosphorus-containing molecular sieves to be prepared by theprocesses of the invention, there may be mentioned more especiallyaluminophosphates and silicoaluminophosphates. As examples of structuretypes produced there may be mentioned more especially molecular sievesof the structure types CHA and LEV. As seeds, there may for example beused crystals of structure type LEV, OFF, and CHA. As specific materialsto be used, there may be mentioned Levyne, ZSM-45, Chabasite, Offretiteand SAPO-34.

The seeds used in the present invention may be obtained by methodsdescribed herein or known in the art or described in the literature.

Manufacture of OFF-structure type seed crystals, in particular colloidalOffretite seeds, may be carried out as described in InternationalApplication No. WO 97/03020, while suitable procedures, includingdetails of synthesis mixtures and hydrothermal treatment, for themanufacture of LEV- and CHA-structure type crystals are described inEP-A-91048, 91049, 107 370, 143 642 and U.S. Pat. No. 4,495,303 (forLEV) and GB-A-868 846 and 2 061 500 and U.S. Pat. Nos. 3,030,181 and4,544,538 (for CHA), the disclosures of all of which are incorporated byreference herein. Manufacture of CHA- and LEV-structure type seedcrystals is advantageously carried out as described in the examplesbelow.

Apart from the presence of the seeds, the synthesis mixture used in thepresent invention is typically one that is known in the art or asdescribed in the literature as suitable for the production of themolecular sieve concerned. This is also the case for the conditions oftreatment, except that the presence of the seeds may make possible thereduction of reaction times or may obviate stirring if that wereotherwise necessary.

In general, the treatment of the synthesis mixture to yield the desiredphosphorus-containing crystalline molecular sieve, usually termedhydrothermal treatment, though strictly that term should be used onlyfor treatments in which there is vapour-phase water present, isadvantageously carried out under autogenous pressure, for example in anautoclave, for example a stainless steel autoclave which may, ifdesired, be ptfe-lined. The treatment may, for example, be carried outat a temperature within the range of from 50, advantageously from 90,especially 120, to 250° C., depending on the molecular sieve being made.The treatment may, for example, be carried out for a period within therange of from 20 to 200 hours, preferably up to 100 hours, againdepending on the molecular sieve being formed. The procedure may includean ageing period, either at room temperature or, preferably, at amoderately elevated temperature, before the hydrothermal treatment atmore elevated temperature. The latter may include a period of gradual orstepwise variation in temperature.

For certain applications, the treatment is carried out with stirring orwith rotating the vessel about a horizontal axis (tumbling). For otherapplications, static hydrothermal treatment is preferred. If desired,the synthesis mixture may be stirred or tumbled during an initial partof the heating stage, for example, from room temperature to an elevated,e.g., the final treatment, temperature, and be static for the remainder.Agitation generally produces a product with a smaller particle size anda narrower particle size distribution than static hydrothermaltreatment.

The seeds are generally present in the synthesis mixture in aconcentration of up to 10000, advantageously at most 3000, moreadvantageously at most 1500, and preferably at most 1000, morepreferably at most 500, and most preferably at most 350 ppm, based onthe total weight of the synthesis mixture. A minimum seeding level isgenerally 1 ppb (0.001 ppm), advantageously at least 0.1, moreadvantageously at least 1, and preferably at least 10, ppm, based on thetotal weight of the synthesis mixture. Advantageous ranges ofproportions are from 1 to 2000, preferably 100 to 1500, and mostpreferably 100 to 250, ppm.

The colloidal seeds are advantageously incorporated in the synthesismixture in the form of a suspension, advantageously in an aqueousmedium, preferably water, or another liquid component of the synthesismixture. Less preferably they may be added in dry, but not calcined,form. It is believed that calcination significantly reduces the activityof small crystallites to act as seeds; similarly any other treatmentthat reduces the seeding activity of materials should be avoided. Asused herein, the term “colloidal”, when used of a suspension, refers toone containing discrete finely divided particles dispersed in acontinuous liquid phase and preferably refers to a suspension that isstable, in the sense that no visible separation occurs or sedimentforms, in a period sufficient for the use intended, advantageously forat least 10, more advantageously at least 20, preferably at least 100,and more preferably at least 500, hours at ambient temperature (23° C.).

The maximum size of the particles for the suspension to remain stable(peptized) will depend to some extent on their shape, on the nature andpH of the continuous medium, as well as on the period during which thesuspension must remain usable. In general, the maximum dimension will be1 μm, advantageously 500, more advantageously 400, preferably 300, morepreferably 200, and most preferably 100, nm. The particles may be ofspherical, columnar, rod, coffin, platelet, or needle shapes. Whereparticles are platelets or needles, the dimension referred to is theirsmallest dimension.

The minimum dimension is such that the particles do not dissolve orre-dissolve in the medium, and for crystallinity they must contain atleast a small plurality, advantageously at least two, preferably four,unit cells of the crystal. The minimum particle size is in general 5,advantageously 10, and preferably 20, nm. Mean particle sizes aregenerally in the range 5 to 1000, advantageously 10 to 300, moreadvantageously 10 to 200, and preferably 20 to 100, nm. Advantageouslyat least 50%, more advantageously at least 80%, and more preferably atleast 95%, by number, of the particles are greater than the givenminima, smaller than the given maxima, or within the given ranges ofparticle size. Measurements of particle size may be effected by electronmicroscopy, for example using a Philips SEM 515 unit.

If the product is desired in small particle size form, a larger numberof smaller sized seeds is desirably employed. The smaller the particlesize of the seeds, the lower the weight percentage that is effective.The crystals are advantageously stirred into the synthesis mixture for atime sufficient to provide a uniform dispersion, this time beingdependent primarily on the viscosity of the synthesis mixture, and alsoon the scale and type of the equipment, but ranging generally from 30seconds to 10 minutes.

More especially, the invention provides processes and uses in whichcolloidal LEV structure type seeds are used in the manufacture of aphosphorus-containing crystalline molecular sieve.

A colloidal suspension of LEV may be obtained by synthesizing a LEVstructure type molecular sieve by hydrothermal treatment of anappropriate synthesis mixture, and separating the product from thesynthesis mixture, washing the product, and recovering the resultingwash liquid.

Examples of the LEV structure type include Levyne, NU-3, ZK-20, ZSM-45and SAPO-35.

The colloidal LEV seeds are especially suitable to provide crystallinemolecular sieves of the CHA structure type. Examples of such CHAmaterials are SAPO-, AlPO-, MeAPO-, MeAPSO-, ElAPSO- and ElAPO-47 andespecially the corresponding-34 materials. In these formulae, Elrepresents magnesium, zinc, iron, cobalt, nickel, manganese, chromium ormixtures of any two or more such elements. CHA structure type seeds mayalso be used in synthesis of these materials. LEV and CHA structure typeseeds may be used in the synthesis of SAPO-, AlPO-, MeAPO-, MeAPSO-,EIAPSO- and EIAPO-materials of the LEV structure type, e.g., the -35materials. Where a material is referred to as, for example, a SAPOmaterial, this terminology includes the possibility that additionalelements may be present, either in the framework or otherwise, as in thecase discussed below, of Ni-SAPO.

Among these materials, SAPO-34 has been found to have considerableutility in catalysing the conversion of methanol to light olefins,primarily those with 2 to 4 carbon atoms (see, for example, U.S. Pat.No. 5,126,308, also incorporated by reference herein). It would be ofvalue to be able to increase the proportion of ethylene in the product.

The present invention accordingly also provides a process for themanufacture of SAPO-34 in which the percentage area contribution ofBroensted acid sites to the total OH area in the IR spectrum is at least30%, advantageously at least 50%, and preferably at least 60%, by aprocedure in which the synthesis mixture contains colloidal crystallinemolecular sieve crystals. In certain embodiments, percentage areacontribution is at most 95%.

More especially, the invention further provides a process for themanufacture of SAPO-34, which comprises treating a synthesis mixturehaving a molar composition appropriate for SAPO-34 formation and alsocontaining colloidal OFF-type, CHA-type, or LEV-type seed crystals,advantageously of mean particle size of at most 400 nm, for a time andat a temperature sufficient to form SAPO-34.

The process of the invention is capable of providing SAPO-34 in whichthe particle size is at most 0.75 μm, advantageously at most 0.5 μm.Advantageously the particle size distribution is such that 80% (bynumber) of the particles are within ±10% of the mean.

In a further aspect, the invention provides a process for the conversionof an oxygenate, especially methanol, to olefins which comprisescontacting the oxygenate with a catalyst under conversion conditions,the catalyst comprising SAPO-34 produced in accordance with theinvention.

The olefins produced are advantageously light olefins, by which is to beunderstood an olefin mixture of which at least 50% by weight containfrom 2 to 4 carbon atoms.

Referring now more especially to the Broensted acid site aspect of theinvention, it is believed (without the invention being limited by anytheoretical considerations) that the Broensted acidity is important inthe catalytic activity, especially in oxygenate to olefin conversion, ofa molecular sieve, and that a molecular sieve in which the bridgedhydroxyl groups represent a high proportion of the hydroxyl groups inthe crystal will have a high activity. Infra-red analysis of a highlyactive product of the invention (described as are the methods ofmeasurement in more detail in the Examples below) shows that in theSAPO-34 OH region, 4000 to 3000 cm⁻¹, two peaks, at ˜3620 and ˜3595cm⁻¹, are the main features, while less active samples show a number ofbands in the range from 3750 to 3620 cm⁻¹, which are assigned to Al—OH,Si—OH, and P—OH groups on an external surface or on an internal defect.

A further IR spectrum characteristic associated with catalytic activityis a high peak intensity in the T-O asymmetric stretch region, at 1050to 1150 cm⁻¹, intensity being indicated by both height and sharpness,i.e., a high level of internal crystallinity. It is accordingly believedthat a correlation exists between high internal crystallinity, orcrystal perfection, and a high contribution of Broensted OH groups tothe total OH content of the material.

Further, in common with many other molecular sieves, the catalyticactivity and stability of activity of SAPO-34 are in general termsgreater the smaller the particle size.

The synthesis mixture for producing SAPO-34 according to the inventionadvantageously has a molar composition, apart from the colloidal seeds,within the following ranges:

P₂O₅:Al₂O₃  0.9 to 1.2:1 SiO₂:Al₂O₃ 0.05 to 0.4:1 H₂O:Al₂O₃   10 to100:1together with an organic template, advantageously tetraethylammoniumhydroxide (TEAOH), dipropylamine (DPA), isopropylamine or morpholine, ora mixture of two or more such templates, in a proportion appropriate toyield SAPO-34. A preferred template mixture comprises TEAOH and DPA.

In a particularly advantageous embodiment of the invention the synthesismixture advantageously contains a source of metallic elements,especially a Group VIII metal, more especially nickel. A convenientsource of the metal is a water-soluble salt, for example the nitrate.The metal is advantageously present in a molar proportion calculated asoxide relative to Al₂O₃ within the range of 0.001 to 0.05, preferably0.005 to 0.01. The presence of nickel enhances the catalytic activity atleast in oxygenate conversion. Other suitable Group VIII metals includeFe and Co, while other suitable metals include Mn, Cr, Cu, Zn, Mg, Tiand Zr.

The sources of the materials may be any of those in commercial use ordescribed in the literature, as may the preparation of the synthesismixture.

The invention also provides the products of the processes and of theuses of the earlier aspects of the invention. The products, if requiredafter cation exchange and/or calcining, have utility as catalystprecursors, catalysts, and separation and absorption media. They areespecially useful in numerous hydrocarbon conversions, separations andabsorptions. They may be used alone, or in admixture with othermolecular sieves, in particulate form, supported or unsupported, or inthe form of a supported layer, for example in the form of a membrane,for example as described in International Application WO 94/25151.Hydrocarbon conversions include, for example, cracking, reforming,hydrofining, aromatization, oligomerisation, isomerization, dewaxing,and hydrocracking (e.g., naphtha to light olefins, higher to lowermolecular weight hydrocarbons, alkylation, transalkylation,disproportionation or isomerization of aromatics). Other conversionsinclude the reaction of alcohols with olefins and the conversion ofoxygenates to hydrocarbons.

Conversion of oxygenates may be carried out with the oxygenate, e.g.,methanol, in the liquid or, preferably, the vapour phase, in batch or,preferably, continuous mode. When carried out in continuous mode, aweight hourly space velocity (WHSV) based on oxygenate, ofadvantageously 1 to 1000, preferably 1 to 100, hour⁻¹ may convenientlybe used. An elevated temperature is generally required to obtaineconomic conversion rates, e.g., one between 300 and 600° C., preferablyfrom 400 to 500° C., and more preferably about 450° C. The catalyst maybe in a fixed bed, or a dynamic, e.g., fluidized or moving, bed.

The oxygenate feedstock may be mixed with a diluent, inert under thereaction conditions, e.g., argon, nitrogen, carbon dioxide, hydrogen, orsteam.

The concentration of methanol in the feedstream may vary widely, e.g.,from 5 to 90 mole percent of the feedstock. The pressure may vary withina wide range, e.g., from atmospheric to 500 kPa.

The following Examples, in which parts are by weight unless otherwiseindicated, illustrate the invention. The source and purity of startingmaterials are those first given, unless indicated otherwise.

EXAMPLE 1

This example illustrates the manufacture of a LEV-type zeolite ofparticle size suitable for use as seeds in the manufacture, inter alia,of phosphorus-containing crystalline molecular sieves.

In a first stage, 15.95 parts of sodium aluminate (Dynamit Nobel, 53%Al₂O₃, 41% Na₂O, 6% H₂O), 19.95 parts of sodium hydroxide (Baker, 98.6%)and 5.58 parts of potassium hydroxide (Baker, 87.4%) were dissolved in151.06 parts of water, and heated to boiling until a clear solution wasobtained. After cooling to room temperature, water loss was compensated,to form Solution A. 270.60 parts of colloidal silica (Ludox HS40, 40%SiO₂) were mixed with 106.12 parts of choline chloride (R, Fluka)forming a viscous mass, and Solution A added with stirring at increasingspeed as the viscosity decreased, together with 190 parts of rinsewater, mixing then continuing for a further 5 minutes. The molarcomposition was:

-   -   1.95 Na₂O:0.24 K₂O:0.46 Al₂O₃:10 SiO₂:4.187 R:155 H₂O.

To 290 parts of this mixture, 0.49 parts of conventional LEV zeoliteseeds were added, and a sample transferred to an autoclave, where it washeated in a 120° C. oven for 144 hours. The product was washed,recovered by centrifuging and dried overnight at 120° C. The productcomprised spherical aggregates of from 2 to 2.5 μm, made up of ˜100 nmparticles, with an X-ray diffraction pattern (XRD) of ZSM-45, a zeoliteof LEV-type structure, as described in EP-A-1O7 370 (Mobil).

The product was used as seeds in the next stage, in which 8.38 parts ofsodium aluminate, 10.53 parts of sodium hydroxide, 2.96 parts ofpotassium hydroxide, and 78.95 parts of water were treated as describedabove to form a Solution A. Solution A was then added to a mixture of142.42 parts of colloidal silica and 55.5 parts of choline chloride,together with 100.00 parts of rinse water and mixed as described above,with the addition of 0.68 parts of the first stage seeds. The reactionmixture was heated in an autoclave at 120° C. for 174 hours, the productrecovered by washing, centrifuging and drying having an XRD similar tothat of the first stage. The second supernatant of the washing procedurewas not clear, and had a pH of 10.3. It was found to be a dispersionwith a solids content of 2.3%. Analysis by scanning electron microscopy(SEM) and XRD showed ˜100 nm unaggregated crystals with a ZSM-45structure, LEV structure type.

EXAMPLE 2

This example illustrates the manufacture of a chabasite dispersionsuitable for use, in turn, for seeding in SAPO-34 manufacture. The seedswere prepared as follows:

A synthesis mixture was prepared as described in the first part ofExample 1, except that as seeds the colloidal sol from the secondsupernatant of the second part of Example 1 was used, at a seeding levelof 0.15% by weight of solids. The seeded synthesis mixture was heated ina stainless steel autoclave for 96 hours at 120° C., with a heat-up timeof 3 hours. The product, recovered by centrifuging and drying, had anXRD pattern corresponding to ZSM-45. The first supernatant was not clearand yielded, after centrifuging at 11000 rpm and further washing, adispersion with solids content 4.6%, of crystals of size about 100 nm,XRD showing the product to be ZSM-45, a LEV structure-type zeolite.

Solution A was prepared as described in Example 1 using the followingcomponents, in the proportions shown:

NaOH 61.66 KOH 28.73 Al(OH)₃(Alcoa, 99.3%) 15.73 H₂O 190.30

300.23 parts of colloidal silica and 168.89 parts of water were pouredinto a mixer, and Solution A added together with 12.65 parts of rinsewater. After mixing for 5 minutes, 16 parts of the 4.6% solids LEVslurry were added. The molar composition of the synthesis mixture was:

-   -   3.8 Na₂O:1.12 K₂₀:0.5 Al₂O₃:10 SiO₂:161 H₂O, with 927 ppm seeds.

The synthesis mixture was heated in an autoclave to 100° C. over 2hours, and maintained at that temperature for 96 hours. After cooling,the content of the autoclave, a milky suspension, was washed five timeswith demineralized water and centrifuged at 9000 rpm. After taking asample for XRD and SEM, the remainder was redispersed to form acolloidal solution, stable over several days, with a solids content of6.4%. The XRD of the product shows it to be chabasite, with a uniformparticle size 100×400 nm.

EXAMPLE 3

This example illustrates the manufacture of SAPO-34 of small particlesize and uniform size distribution.

A synthesis mixture was prepared from the following components in theproportions shown.

Solution Component Proportion A Al₂O₃ (Pural SB Condea 75%) 68.18 H₂O100.02 B H₃PO₄ (Acros, 85%) 115.52 H₂O, 80.27 C Colloidal Silica (LudoxAS40) 22.73 H₂O, rinse 10.20 D TEAOH (Eastern Chemical, 40%) 182.85 EDPA (Fluka) 80.23 F Seeds, 4.6 Wt. % LEV 31.95

Slurry A was prepared in a mixer, and Solution B added, when a viscoussolution resulted. After leaving the solution to rest for 2 minutes,26.84 parts of rinse water were added. After mixing the paste for 6minutes, C was added, and mixed for 2 minutes before adding Solution D.Upon adding E with 70.72 parts of rinse water two phases were formed.After a further 3 minutes mixing a visually homogeneous solutionresulted and after a further 10 minutes mixing the seeds F were added.The molar composition was:

-   -   Al₂O₃:P₂O₅:0.3 SiO₂:TEAOH:1.6 DPA:56 H₂O.+1860 ppm by weight LEV        seeds.

The seeded gel was heated for 60 hours at 175° C. in a stainless steelautoclave. The solid product was recovered by centrifugation, washed 11times with water to a conductivity of about 18 μm, and dried at 120° C.XRD and SEM showed a pure SAPO-34 product with crystals between 0.2 and1.3 μm, with a few crystals between 2 and 3 μm. Chemical analysisindicated a product of molar composition:

-   -   Al₂O₃:0.99P₂O₅:0.36 SiO₂.

In a similar manner a synthesis mixture was prepared from the followingcomponents in the proportions shown.

Solution Component Proportion A Al₂O₃ (Pural SB Condea 75%) 68.06 H₂O100.15 B H₃PO₄ (Acros, 85%) 115.74 H₂O, including rinse 104.92 CColloidal Silica (Ludox AS40) 22.50 H₂O, rinse 10.20 D TEAOH (EasternChemical, 40%) 183.31 H₂O, rinse 43.17 E DPA (Fluka) 80.79 H₂O, rinse26.27

Slurry A was prepared in a mixer, and Solution B added, when a viscousmixture resulted. After mixing for 6 minutes, Solution C was added, andmixed for 2 minutes before adding Solution D which was mixed in for 5minutes. When E was added, two phases were formed. After a further 15minutes mixing a visually homogeneous mixture resulted. The molarcomposition was:

-   -   Al₂O₃:P₂O₅:0.3 SiO₂:TEAOH:1.6 DPA:52 H₂O.

The synthesis solution was divided, and to one sample a 6.4% slurry ofCHA zeolite, prepared as described in Example 2, was added to give aseeding level 410 ppm, the other sample remaining unseeded.

The unseeded sample was heated in a stainless steel autoclave at 175° C.for 60 hours. The seeded sample was divided, one part being heated,without stirring, in a ptfe-lined autoclave for 60 hours at 175° C., andthe other being heated with tumbling in a stainless steel autoclave for60 hours at 175° C.

The samples were allowed to cool, and the product recovered by washingand drying at 120° C. In all cases, a pure SAPO-34 product was obtained,with a molar chemical constitution and crystal sizes as follows:

Unseeded: Al₂O₃: 0.91 P₂O₅: 0.33 SiO₂, 1 to 10 μm Seeded, static: Al₂O₃:0.89 P₂O₅: 0.31 SiO₂, 0.2 to 1.5 μm Seeded, tumbled: Al₂O₃: 0.91 P₂O₅:0.35 SiO₂, ~0.5 μm.

The benefits of reduced crystal size and size distribution of seedingwith colloidal chabasite seeds are apparent, especially when combinedwith tumbling.

EXAMPLE 4

This example illustrates the use of colloidal Offretite seeds in themanufacture of SAPO-34. The colloidal Offretite was prepared asdescribed in Example 2 of WO 97/03020. A synthesis mixture was preparedas described in Example 3, with the following molar composition:

-   -   Al₂O₃:P₂O₅:0.3 SiO₂:TEAOH:1.6 DPA:51 H₂O.

To this was added a portion of a 5.36% solids content colloidaloffretite slurry (crystal size below 100 nm) to give a seeding level of203 ppm. Hydrothermal treatment and product recovery were carried out asdescribed in Example 3. The product obtained was pure SAPO-34, theparticle size of crystals being mainly between 0.2 and 1.3 μm, with afew crystals between 2 and 3 μm present.

COMPARATIVE EXAMPLE A

This example illustrates the use of powdered LEV, contaminated with someOffretite, in SAPO-34 manufacture. To the same synthesis mixtureprepared for use in Example 4 were added a LEV powder in a proportion togive a seed level of 217 ppm. The powder was mixed into the synthesismixture gel by shaking the gel in a polypropylene bottle for 2 minutes.Hydrothermal treatment and product recovery were carried out asdescribed in Example 4. The product was pure SAPO-34, with the majorityof the crystals of size between 0.5 and 2.5 μm. Comparison of thisexample with Example 4 shows that colloidal seeds at approximately thesame weight ratio yield smaller crystals.

EXAMPLE 5

In this example, the effect of seeding on Ni-SAPO 34 manufacture wasexamined. The synthesis mixture was prepared as in Example 3, exceptthat sufficient nickel nitrate (Ni(NO₃)₂6H₂O, Fluka) was added toSolution A to give a synthesis mixture of molar composition:

-   -   Al₂O₃:P₂O₅:0.3 SiO₂:0.0075 NiO:TEAOH:1.6 DPA:50 H₂₀.

The mixture was divided into two parts, one being seeded with CHAslurry, 6.4% solids content, to a seeding level of 409 ppm. The seededand unseeded samples were each heated in a stainless steel autoclave for60 hours at 175° C. After cooling, the products were recovered, washed,and dried at 120° C. In both cases, a pure SAPO-34 phase was recovered,with molar chemical constitutions and crystal sizes as follows:

Unseeded: Al₂O₃: 0.88 P₂O₅: 0.36 SiO₂: 0.0040 NiO, 1 to 10 μm Seeded:Al₂O₃: 0.84 P₂O₅: 0.31 SiO₂: 0.0042 NiO, 0.2 to 1.5 μm.

Again, the benefit of seeding in producing smaller crystals is apparent.

The two samples made as described above were examined by diffusereflectance FTIR to establish their crystal quality and Broenstedacidity. The IR spectra were obtained in a conventional high temperatureDRIFT cell using KBr diluted samples (about 4% sample in dry KBr), thesamples being dehydrated before testing at 200 to 300° C. under vacuum.The spectra, obtained using 64 scans at 4 cm⁻¹ resolution, were analysedusing Gaussian-Lorentzian peaks to determine locations and relativeareas and shapes.

The spectra of the seeded and unseeded products of the example wereinspected in the region between wave numbers 1400 and 1000 cm⁻¹ and themain peaks attributable to framework T-O stretching were measured. Inthe Table below are set out the centre locations, peak heights and peakwidths (C, H, W) of the three main bands in the region.

C, H, W C, H, W C, H, W Seeded 1106/8.7/51 1135/12.3/54.7 1179/6.7/65.5Unseeded 1082/1.4/90 1129/2.1/71 1190/0.9/90.6

The seeded sample has, as is apparent from the Table, by far the highestand sharpest peaks, and hence the highest internal crystallinity.

The sole figure of the accompanying drawings shows the region betweenwave numbers 3800 and 3450 cm⁻¹.

Referring now to the figure, the locations, heights and widths of themain peaks attributable to the bridged hydroxyl groups are shown for thesamples. The band at ≈3620 is attributed to undisturbed Broensted OHgroups in 8-membered rings while that at ≈3595 is attributed to such OHgroups interacting with framework oxygen or OH groups located in the6-membered rings. Measurement of the contribution (by area) of thesebands to the total area in the OH region gives the results in the Tablebelow:

Sample % Area Contribution Seeded 62 Unseeded 21

Clearly, the seeded sample has the higher percentage area contributionfrom the Broensted acid sites, despite the fact that this sample has alower particle size, and hence a larger surface/volume ratio. From thisit is tentatively concluded that the remaining peaks in the 3800 to 3620cm⁻¹ range are associated with internal defects rather than surfacehydroxyl groups, and postulated that products with high percentage areacontribution of Broensted acid OH groups to the total OH area arematerials with a high level of internal crystal perfection.

EXAMPLE 6

This example illustrates the use of CHA seeds in the manufacture ofSAPO-34 with a silicon content different from that of Example 3. Thesynthesis solution was prepared as described in Example 3, but withcomponents in proportions to give the following molar composition:

-   -   Al₂O₃:P₂O₅:0.1 SiO₂:TEAOH:1.6 DPA:52 H₂O.

A slurry of 6.4% solids content of CHA seeds was added to give a seedcontent of 397 ppm.

The mixture was hydrothermally treated as described in Example 3, andthe product recovered in the same way. It was pure SAPO-34, with mostcrystals in the range 0.2 to 1.5 μm, with a few crystals of size in the2 to 4 μm range also present. The product analysed as

-   -   Al₂O₃:0.79 P₂O₅:0.21 SiO₂.

EXAMPLE 7

Example 6 was repeated, except that the silica content was varied togive a molar composition of the synthesis mixture of:

-   -   Al₂O₃:P₂O₅:0.45 SiO₂:TEAOH:1.6 DPA:52 H₂O with 397 ppm CHA        seeds.

The hydrothermal treatment was as described in Example 3; the productwas pure SAPO-34 of particle size between 0.2 and 1.5 μm. Chemicalanalysis:

-   -   Al₂O₃:0.92 P₂O₅:0.42 SiO₂.

The yields from Examples 6 and 7, and the static seeded part of thesecond part of Example 3, the synthesis mixtures of which differedprimarily in their silicon contents, were as follows:

-   -   Example 6, 0.1 SiO₂; yield 7.8% 3, 0.3 SiO₂; yield 12.5% 7, 0.45        SiO₂; yield 12.7%.

COMPARATIVE EXAMPLE B

In Examples 5 to 7, hydrothermal treatment was carried out in a staticautoclave. In this and following examples, the influences of stirringand tumbling on the properties of SAPO-34 were examined, this exampleemploying an unseeded synthesis mixture of a molar composition similarto that of the second part of Example 3, but with 51 moles of H₂O ratherthan 52. Hydrothermal treatment was carried out by heating the synthesismixture in a stainless steel autoclave from room temperature to 175° C.over 6 hours, with stirring at 120 rpm, and maintained at 175° C. for 60hours with continued stirring. Recovery was as described in Example 3.The product was a mixture of SAPO-34, SAPO-18, with some SAPO-5, thecrystals being within the range of 0.2 to 1 μm.

EXAMPLE 8

This example illustrates the effect of stirring an Offretite seededsynthesis mixture during hydrothermal treatment. Colloidal (<100 nm)Offretite seeds were added from a 5.36% solids content Offretite slurry,the resulting molar composition of the seeded mixture being:

-   -   Al₂O₃:P₂O₅:0.3 SiO₂:TEAOH:1.6 DPA:54H₂O plus 0.19 weight %        seeds.

The synthesis mixture was divided into two parts. One part (A) wasplaced in a stainless steel autoclave equipped with a 120 rpm stirrerand heated from room temperature to 175° C. over 6 hours with stirring,and maintained at 175° C. for 60 hours with continued stirring. A secondpart (B) was heated without stirring from room temperature to 175° C.over 2 hours, and maintained at 175° C. for 48 hours, with a sample (C)being taken at 24 hours. After recovery and drying, the products wereanalysed by SEM and XRD.

-   -   Sample A: SAPO-34, contaminated with SAPO-18 and some SAPO-5,        crystals between 0.2 and 1.0 μm.    -   Sample B: Pure SAPO-34, with crystal size 0.5 to 2 μm.    -   Sample C: SAPO-34 with some amorphous material, crystals between        0.2 and 1.5 μm.

EXAMPLE 9

This example illustrates the effect on Ni-SAPO-34 manufacture ofagitation during the warm-up period of hydrothermal treatment, followedby static heat-soaking. A nickel-containing synthesis mixture wasprepared, following the procedure described in Example 4, to produce amixture of molar composition:

-   -   Al₂O₃:P₂O₅:0.3 SiO₂:0.0076 NiO:TEAOH:1.6 DPA:52H₂O.

The mixture was divided into two parts, of which one, sample A, wasseeded with the CHA seeding slurry used in Example 5 to give a seedcontent of 202 ppm, the other, sample B, remaining unseeded. Bothsamples were transferred to stainless steel autoclaves, which wereplaced in an oven and mounted on a horizontal shaft rotatable at 60 rpm.The autoclaves were tumbled for a 2 hour period of heating to 175° C.;tumbling then ceased and the temperature kept at 175° C. for 60 hours.

After cooling, the products were recovered by centrifugation, washed,and dried at 120° C. XRD showed that both products were pure Ni-SAPO-34.Sample A comprised crystals of particle size about 1 μm, with damagedsurfaces. Sample B comprised crystals of size ranging up to 10 μm, manycrystals being fragmented.

The example shows that seeding is required to bring the particle sizedown to the desired levels even with initial tumbling.

EXAMPLE 10

This example illustrates the use of a SAPO-34 seed slurry in SAPO-34manufacture.

To a synthesis mixture of the molar composition set out in the secondpart of Example 3 was added a 10% slurry of SAPO-34, prepared asdescribed in the second part of Example 3 with tumbling, to give aseeding level of 0.1% (1000 ppm). The seeded mixture was heated in astainless steel autoclave at 175° C. for 48 hours. The mixture wasallowed to cool, and the product recovered and identified as pureSAPO-34 with crystal sizes ranging from 0.5 to 4 μm. The exampleillustrates that while colloidal SAPO-34 crystals are effective inSAPO-34 manufacture they are not as effective as CHA or LEV structuretype zeolite seeds.

EXAMPLE 11

In this example the effectiveness in catalysing the methanol to olefinconversion of the products made and discussed in Example 5 was measured.In a bench scale fixed bed reactor maintained at 450° C. methanoldiluted with nitrogen (total pressure-atmospheric, partial pressure ofmethanol 0.12) was passed over a catalyst at WHSV (based on methanol) of1 hr⁻¹ and a GHSV (based on methanol plus nitrogen) of about 5500 hr⁻¹.After 1 hour on stream at 100% methanol conversion, the results were asshown in the Table.

Yield, % Seeded Unseeded C₂ = 50.1 47.9 C₃ = 28.0 33.4 C₂ = +C₃ = +C₄ =85.6 91.4 C₁ to C₄ sats. 11.0 6.1

The yield of the more desirable ethylene is increased by about 5% usingthe product obtained with seeding compared with the unseeded product.

1. A process for the manufacture of a crystalline molecular sievecontaining phosphorus in its framework, which process comprises treatinga synthesis mixture comprising a source of aluminum, a source ofphosphorus, an organic template, and colloidal crystalline molecularsieve seeds for a time and at a temperature sufficient to form thecrystalline molecular sieve, wherein the phosphorus-containing molecularsieve is selected from the group consisting of aluminophosphates andsilica-aluminophosphates.
 2. A process as claimed in claim 1, whereinthe phosphorus-containing molecular sieve is of the CHA or LEV structuretype.
 3. A process as claimed in claim 1, wherein thephosphorus-containing molecular sieve is SAPO-34.
 4. A process asclaimed in claim 3, wherein the SAPO34 is Ni-SAPO-34.
 5. A process asclaimed in claim 3, wherein the percentage area contribution ofBroensted acid sites to the total OH area in the IR specs is at least30%.
 6. A process 5 as claimed in claim 5, wherein said contribution isat least 50%.
 7. A process as claimed in claim 1, wherein the seeds areof structure type LEV, OFF, or CHA.
 8. A process as claimed in claim 1,wherein the seeds are of Levyne, ZSM-45, Chabasite, Offretite, orSAPO-34.
 9. A process as claimed in claim 1, wherein the seeds arepresent in a proportion within the range of 1 to 2000 ppm, based on thetotal weight of the synthesis mixture.
 10. A process as claimed in claim9, wherein the proportion is within the range of from 100 to 1500 ppm.11. A process as claimed in claim 9, wherein the proportion is withinthe range of from 100 to 250 ppm.
 12. A process as claimed in claim 1,wherein the seeds are incorporated in the synthesis mixture in the formof a suspension.
 13. A process as claimed in claim 1, wherein theparticle size of the seeds is within the range of from 5 to 1000 nm. 14.A process as claimed in claim 13, wherein the particle size is withinthe range of from 10 to 300 nm.
 15. A process as claimed in claim 13,wherein the particle size is within the range of from 20 to 100 nm. 16.A process as claimed in claim 1, wherein the phosphorus-containingmolecular sieve is of a first structure type and the seeds are of asecond structure type.
 17. A process as claimed in claim 16, wherein thefirst structure type is CHA and the second structure type is LEV. 18.The molecular sieve product of the process as claimed in claim 1wherein, within said molecular sieve product, the percentage areacontribution of Broensted acid sites to the total OH area in the IRspectrum is at least 30%.
 19. The molecular sieve of claim 18, inparticulate or layer form.
 20. SAPO-34 in which the percentage areacontribution of Broensted acid sites to the total OH area in the IRspectrum is at least 30%.
 21. A process for the conversion of anoxygenate to olefins which comprises contacting the oxygenate undercatalytic conversion conditions with the molecular sieve of claim 18.22. A process for the conversion, adsorption or separation ofhydrocarbons which comprises contacting the hydrocarbons with themolecular sieve of claim 18, optionally after washing, cation exchange,or calcining.
 23. A process for the synthesis of a phosphorus-containingcrystalline molecular sieve which comprises treating a synthesis mixturewith colloidal crystalline molecular sieve seed crystals to control theparticle size of the phosphorus-containing molecular sieve and/or theacceleration of the formation of the phosphorus-containing crystallinemolecular sieve during synthesis, wherein the phosphorus-containingmolecular sieve is selected from the group consisting ofaluminophosphates and silica-aluminophosphates.